Chlorofluorocarbon-type gases have been used as a cooling medium in an air conditioner, a freezer, and the like. However, the chlorofluorocarbon-type gas acts to harm the ozone layer and has an adverse effect on the environment disadvantageously.
Therefore, a magnetic refrigeration system has recently been proposed as a substitute for a conventional gas refrigeration system using the cooling medium of the chlorofluorocarbon-type gas having the environmental problem. The magnetic refrigeration system employs a magnetic refrigeration material as a refrigerant, and utilizes a magnetic entropy change, which occurs when the magnetic order of the material is changed by a magnetic field under an isothermal condition, and an adiabatic temperature change, which occurs when the magnetic order of the material is changed by a magnetic field under an adiabatic condition. Thus, the magnetic refrigeration system can achieve the refrigeration without using the chlorofluorocarbon gas, and has a higher refrigeration efficiency than that of the conventional gas refrigeration system advantageously.
In a practical use of the magnetic refrigeration material, it is necessary to form powder particles of the magnetic refrigeration material into a shape suitable for the refrigeration system to prepare a magnetic refrigeration module.
Patent Publication 1 discloses a method for producing a magnetic LaFeSiH material. In this method, magnetic particles are coated with a film of Sn or an Sn alloy, and then the particles are bonded to each other by a heat treatment at 100° C. to 300° C. in an inert gas atmosphere.
Patent Publication 2 discloses a method for producing a magnetic refrigeration material. In this method, an La(Fe,Si)13 alloy powder is shaped by a spark plasma sintering process at a sintering temperature of 950° C. to 1200° C.